Optical information recording medium, and substrate and manufacturing method for the optical information recording medium

ABSTRACT

In an optical disk including at least a rewritable phase change material and comprising a recording layer having a reflectivity of more than 15%, an address output value as an address pit signal component occupying in a reproduced signal in a non recording state is prescribed to be 0.18 though 0.27 or a numerical aperture of an address pit signal occupying in a reproduced signal in a non recording state is prescribed to be more than 0.3.

This application is a Continuation of co-pending application Ser. No.09/695,866, filed on Oct. 26, 2000, and for which priority is claimedunder 35 U.S.C. § 120; and this application claims priority ofApplication No. 11-334098 filed in Japan on Nov. 25, 1999, andApplication No. 11-341821 filed in Japan on Dec. 1, 1999, under 35U.S.C. § 119; the entire contents of all are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical information recording mediumbeing utilized for a recording and reproducing apparatus or a drive,which records an information in the optical information recording mediumwith moving the medium relatively and reads out the information from themedium, and a substrate and a manufacturing method for the opticalinformation recording medium, particularly, relates to an opticalinformation recording medium, which can be recorded and reproduced in ahigh density and a large capacity, and a substrate and a manufacturingmethod for the optical recording medium.

2. Description of the Related Art

Currently, there existed a system, which can optically record andreproduce information by using a disk shaped medium, as a system of aninformation recording medium for reading out information with moving themedium relatively. A disk system medium can be divided into severaltypes such as a read only type or a ROM (read only memory) type, arecordable or a write once type or an “R” type and a rewritable type ora RW type. Generally, a recording density of a medium is high in a ROMtype and low in “R” and RW types. For instance, in a DVD (digitalversatile disk) system, which utilizes a laser beam having a wavelengthof 635 through 650 nm, introduced into the market in 1996, a read onlytype disk such as a DVD-ROM disk and a DVD-Video disk was introducedfirst. A recording capacity of a read only type DVD disk is 4.7 GB. Onthe other hand, a recording capacity of a rewritable type DVD disk suchas a DVD-RAM (DVD-Random Access Memory) disk is 2.6 GB, that is, therecording capacity of a DVD-RAM disk is almost 55% of that of a DVD-ROMdisk. Researches and developments for increasing a recording capacity ofa rewritable type disk are progressing. However, a system having a samecapacity as that of a DVD-ROM disk has not been developed yet.

In the case of a rewritable type disk, a recording format on a disk andmaterials of recording medium are key technologies. In a DVD-RAM disk, aland-groove recording method, which is utilized for recordinginformation on both land and groove of an optical information recordingmedium, has been used. In this method, an address necessary to recordingand reproducing is recorded with cutting a land and a groove at eachspecific period of time.

FIG. 19 is a fragmentary plan view of a disk partially enlarging amicroscopic construction 20, that is, a physical format construction ofthe land-groove recording method disk. In FIG. 19, the drawing shows anexternal appearance of the construction when the disk is not recordedand grooves 21 a through 21 c, hereinafter represented by the groove 21,are formed in parallel to each other. Lands 22 a and 22 b, hereinafterrepresented by the land 22, are allocated in between the grooves. Aninformation is recorded on both the groove 21 and the land 22 whenrecording. A plurality of address pits 23 a through 23 n, which isnecessary to recording and reproducing, is formed by cutting the groove21 and land 22. The addresses occupy an area 24 in conjunction with anaccompanied signal, so that the area 24 prevents a total capacity of adisk from increasing. In other words, a limited area of a disk can notbe effectively utilized because of the area 24.

Further, with respect to recording material, in consideration ofinterchangeability with a read only type DVD disk drive, a phase changerecording method, which does not utilize a magnetic head, is suitable.However, this method is defective in reflectivity, which is muchinferior to a read only type disk or a write once type disk of utilizingdye. Accordingly, the low reflectivity results in that a recordingcapacity can not be increased.

By combining a microscopic construction or a physical formatconstruction with a phase change material for high density recording andby optimizing them, a recording capacity equivalent to that of a readonly type DVD disk can be realized.

An optical disk, which records addresses with scattering over a diskwithout having an inherent address area such as the area 24 shown inFIG. 19, is considered as a format for a large capacity optical disk. Inother words, an address area such as the area 24 is not provided, sothat a recording capacity can be increased as many as that of a DVD-ROMdisk. However, in a case that a main recording signal is recorded in avicinity area of an address signal, the main recording signal mayinterfere in the address signal and an error may occur by this method,and then rewriting can not be performed any more. Conversely, theaddress signal may leak into and interfere in the main recording signaland result in a reading out error.

SUMMARY OF THE INVENTION

Accordingly, in consideration of the above-mentioned problems of theprior art, an object of the present invention is to provide an opticalinformation recording medium of a high density phase change type, thatis, a recording disk, which can record and reproduce a main recordingsignal and an address signal without interfering in each other,particularly, to indicate an output range of an address signal forrealizing the object and a dimension of a microscopic construction ofsuch the address signal in detail.

Further, the high density phase change type medium is not limited to aDVD disk. Accordingly, dimensions of a microscopic construction areindicated in a general equation for being applied to a recording andreproducing apparatus, under developing, which utilizes a laser beamhaving a shorter wavelength.

Furthermore, another object of the present invention is to provide anoptical information recording disk of a high density phase change typeor a recording disk comprising both a recording/reproducing area andanother area having a pit array for preventing the disk from illegalduplication and an address signal mentioned above so as to be able torecord and reproduce with minimizing relative interference between amain recording signal and an address signal, moreover, so as to indicatea performance range of an address signal, wherein the address signal canbe read out properly when the recording disk is not recorded, and adimension of microscopic construction of the address signal in detail.

In order to achieve the above object, the present invention provides,according to a first aspect thereof, an optical information recordingmedium comprising: a substrate formed with an area having sinusoidallydeflected grooves and address pits scattered and allocated between thegrooves; a recording layer having reflectivity of more than 15% beingcomposed of at least a rewritable phase change material; and a resinlayer formed over said recording layer, the optical informationrecording medium is further characterized in that an output value ofaddress pit as a signal component of address pit occupying in areproduced signal under a not recorded condition in the area is within arange of 0.18 to 0.27.

According to a second aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected grooves and address pits scatteredand allocated between the grooves; a recording layer having reflectivityof 18 through 30% being composed of at least a rewritable phase changematerial; and a resin layer formed over the recording layer, the opticalinformation recording medium is further characterized in that an outputvalue of address pit as a signal component of address pit occupying in areproduced signal under a not recorded condition in the area is within arange of 0.18 to 0.27.

According to a third aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected grooves and address pits scatteredand allocated between the grooves of which a track pitch TP is 0.74 μm;a recording layer having reflectivity of 18 through 30% being composedof at least a rewritable phase change material; and a resin layer formedover the recording layer, the optical information recording medium isfurther characterized in that an output value of address pit as a signalcomponent of address pit occupying in a reproduced signal by using apickup having a wavelength of a laser beam of 650 nm and a numericalaperture of 0.6 under a not recorded condition in the area is within arange of 0.18 to 0.27.

According to a fourth aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays; a recording layer havingreflectivity of more than 15% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the optical information recording medium is further characterizedin that an output value of address pit as a signal component of addresspit occupying in a reproduced signal under a not recorded condition inthe area is more than 0.3.

According to a fifth aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays; a recording layer havingreflectivity of 18 through 30% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the optical information recording medium is further characterizedin that an output value of address pit as a signal component of addresspit occupying in a reproduced signal under a not recorded condition inthe area is more than 0.3.

According to a sixth aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays of which a track pitchTP2 is 0.74 μm; a recording layer having reflectivity of 18 through 30%being composed of at least a rewritable phase change material; and aresin layer formed over the recording layer, the optical informationrecording medium is further characterized in that an output value ofaddress pit as a signal component of address pit occupying in areproduced signal by using a pickup having a wavelength of a laser beamof 650 nm and a numerical aperture of 0.6 under a not recorded conditionin the area is more than 0.3.

According to a seventh aspect of the present invention, there providedan optical information recording medium comprising: a substrate formedwith an area having sinusoidally deflected grooves and address pitsscattered and allocated between the grooves; a recording layer havingreflectivity of more than 15% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the substrate is further characterized in that the area isprovided with a microscopic construction being simultaneously satisfiedby relationships among a groove depth “d”, a groove width “w”, a groovetrack pitch TP, an address pit length AL, a readout wavelength λ and asubstrate refractive index “n” in said area such as 0.05 λ/n≦d≦0.1 λ/n,0.35≦w/TP≦0.55, 0.18<0.14k+4.11 n(d−26)/λ<0.27 and k=AL/ML.

According to an eighth aspect of the present invention, there providedan optical information recording medium comprising: a substrate formedwith an area having sinusoidally deflected grooves and address pitsscattered and allocated between the grooves; a recording layer havingreflectivity of 18 through 30% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the substrate is further characterized in that the area isprovided with a microscopic construction being simultaneously satisfiedby relationships among a groove depth “d”, a groove width “w”, a groovetrack pitch TP, an address pit length AL, a readout wavelength λ and asubstrate refractive index “n” in the area such as 0.05 λ/n≦d≦0.1 λ/n,0.35≦w/TP≦0.55, 0.18<0.14k+4.11 n(d−26)/λ<0.27 and k=AL/ML.

According to a ninth aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected grooves and address pits scatteredand allocated between the grooves; a recording layer having reflectivityof 18 through 30% being composed of at least a rewritable phase changematerial; and a resin layer formed over the recording layer, thesubstrate is further characterized in that the area is provided with amicroscopic construction being simultaneously satisfied by relationshipsamong a groove depth “d”, a groove width “w”, a groove track pitch TP,an address pit length AL in the area such as TP=0.74 μm, 20≦d≦41 nm,0.26≦w≦0.41 μm and 35AL+d<53.

According to a tenth aspect of the present invention, there provided anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays; a recording layer havingreflectivity of more than 15% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the substrate is further characterized in that the area isprovided with a microscopic construction being simultaneously satisfiedby relationships among a pit depth “d2”, a pit width “w2”, a pit arraytrack pitch TP2, an address pit length AL2, a readout wavelength λ and asubstrate refractive index “n” in the area such as 0.05 λ/n≦d2≦0.1 λ/n,0.35≦w2/TP2≦0.55, 0.18<0.14k+4.11 n(d2−26)/λ<0.27 and k=AL2/ML.

According to an eleventh aspect of the present invention, there providedan optical information recording medium comprising: a substrate formedwith an area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays; a recording layer havingreflectivity of 18 through 30% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the substrate is further characterized in that the area isprovided with a microscopic construction being simultaneously satisfiedby relationships among a pit depth “d2”, a pit width “w2”, a pit arraytrack pitch TP2, an address pit length AL2, a readout wavelength λ and asubstrate refractive index “n” in the area such as 0.05 λ/n≦d2≦0.1 λ/n,0.35≦w2/TP2≦0.55, 0.18<0.14k+4.11 n(d2−26)/λ<0.27 and k=AL2/ML.

According to a twelfth aspect of the present invention, there providedan optical information recording medium comprising: a substrate formedwith an area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays; a recording layer havingreflectivity of 18 through 30% being composed of at least a rewritablephase change material; and a resin layer formed over the recordinglayer, the substrate is further characterized in that the area isprovided with a microscopic construction being simultaneously satisfiedby relationships among a pit depth “d2”, a pit width “w2”, a pit arraytrack pitch TP2, an address pit length AL2 in the area such as TP2=0.74μm, 20≦d2≦41 nm, 0.26≦w2≦0.41 μm and 44<35AL2+d2<53.

According to a thirteenth aspect of the present invention, thereprovided a substrate for an optical information recording medium, whichis formed with a first area having sinusoidally deflected grooves andaddress pits scattered and allocated between the grooves together with asecond area having sinusoidally deflected pit arrays and address pitsscattered and allocated between the pit arrays, the substrate is furthercharacterized in that the first area is provided with a firstmicroscopic construction being simultaneously satisfied by relationshipsamong a groove depth “d”, a groove width “w”, a groove track pitch TPand an address pit length AL in the first area such as TP=0.74 μm,20≦d≦41 nm, 0.26≦w≦0.41μm and 44<35AL+d<53, and that the second area isprovided with a second microscopic construction being simultaneouslysatisfied by relationships among a pit depth “d2”, a pit width “w2”, apit track pitch TP2 and an address pit length AL2 in the first area suchas TP2=0.74 μm, 20≦d2≦41 nm, 0.26≦w2≦0.41 μg m and 44<35AL2+d2<53.

According to a fourteenth aspect of the present invention, thereprovided a manufacturing method for an optical information recordingmedium comprising steps of: vacuum filming a recording layer beingcomposed of at least a rewritable phase change material on a substrate;and adhering a dummy substrate on said recording layer with sandwichinga resin layer between the recording layer and dummy substrate.

Other object and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an optical information recording mediumaccording to an embodiment of the present invention.

FIG. 2 is a fragmentary plan view of a microscopic construction or aphysical format of the optical information recording medium partiallyenlarged according to the embodiment of the present invention.

FIG. 3 is another fragmentary plan view of a physical format of theoptical information recording medium partially enlarged according to theembodiment of the present invention.

FIG. 4 shows a relation between a depth (d) of a groove and an output(PPb) of a push-pull signal.

FIG. 5 shows a jitter value measured in response to a depth and a widthof the groove.

FIG. 6 shows a model of a four-division detector.

FIG. 7 shows a reproduced waveform in a state of not recorded.

FIG. 8 shows a reproduced waveform in a recorded state.

FIG. 9 shows a measured error rate of an address pit.

FIG. 10 shows a measured error rate of a recorded mark.

FIG. 11 shows a relationship between an output value (APb) of an addresspit and “k” wherein the “k” is obtained by such that an address pitlength (AL) divided by a recorded mark length (ML).

FIG. 12 shows a relationship between an address pit length (AL) and anoutput value (APb) of an address pit.

FIG. 13 shows a relationship between an output value (APb) of an addresspit and “k” wherein the “k” is obtained by such that an address pitlength (AL) divided by a recorded mark length (ML).

FIG. 14 is a cross sectional view of the optical disk shown in FIG. 1.

FIG. 15 is a cross sectional view of an optical disk according to thefirst and a third and a fourth embodiments of the present invention.

FIG. 16 is a cross sectional view of an optical disk according to asecond embodiment of the present invention.

FIG. 17 shows a physical construction format as one example of anaddress information.

FIG. 18 is a flow chart of a manufacturing method of an opticalinformation recording medium according to the present invention.

FIG. 19 is a fragmentary plan view of a microscopic construction or aphysical format of a land-groove type disk partially enlarged accordingto the prior art.

FIG. 20 is a plan view of an optical information recording mediumaccording to an embodiment of the present invention.

FIG. 21 is a fragmentary plan view of a microscopic construction or aphysical format of the optical information recording medium partiallyenlarged according to the embodiment of the present invention.

FIG. 22 shows a reproduced waveform at a microscopic construction in astate of not recorded.

FIG. 23 shows a measured error rate of an address pit.

FIG. 24 is a cross sectional view of an optical disk according to afifth embodiment of the present invention.

FIG. 25 is a plan view of an optical information recording mediumaccording to the fourth and fifth embodiments of the present invention.

FIG. 26 is a flow chart of the manufacturing method of the optical diskaccording to the first through fourth embodiments.

FIG. 27 is a flow chart of the manufacturing method of the optical diskaccording to the fifth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention establishes a method, which is valid in a systemutilizing a laser beam having a shorter wavelength of less than 600 nm,in conjunction with realizing a rewritable type optical disk having ahigher recording capacity, that is, 4.7 GB equivalent to that of a readonly type DVD (digital versatile disk) utilizing a laser beam forrecording and reproducing having a wavelength of 635 through 650 nm.

Prior to depicting each embodiment of the present invention, detailscommon to each embodiment are explained first.

FIG. 1 is a perspective view of an optical disk as an opticalinformation recording medium according to an embodiment of the presentinvention.

FIG. 14 is a cross sectional view of the optical disk shown in FIG. 1.

In FIG. 1, an optical disk 1 is a type of optical disk, which isrecorded with information only in a groove 11. The groove 11 as aninformation track and an address pit, not shown, are embedded in theoptical disk 1 coaxially or spirally and they form a microscopicconstruction 10. A cross sectional view of the optical disk 1 is shownin FIG. 14.

FIG. 14 shows a fundamental construction of an optical disk according tothe embodiment of the present invention. In FIG. 14, the optical disk 1comprises a substrate 2, a recording layer 3 and a resin layer 4 andthey are laminated in order. Recording and reproducing information inthe optical disk 1 by a light beam is performed toward the recordinglayer 3. It is defined arbitrarily that a laser beam having a wavelengthof λ nm, which is stopped down by a objective lens having a numericalaperture of NA, is irradiated on the recording layer 3 from either sideof the optical disk 1. In other words, it is arbitrarily defined whetherthe laser beam is irradiated on a surface of the substrate 2 or theresin layer 4. A path for an incident light, that is, a light path has acertain refractive index “n” to the wavelength λ and an effectiveoptical length of the light path is defined by the refractive index “n”.In FIG. 14, the substrate 2 is illustrated as a light path for oneexample. The microscopic construction 10 including the groove 11 isembedded inside of the optical disk 1, actually formed on a surface ofthe substrate 2. The substrate 2 and the recording layer 3 are formed inparallel to each other.

FIG. 2 is a fragmentary plan view of a microscopic construction or aphysical format of the optical disk 1 shown in FIG. 1, partiallyenlarged, and shows typically a state of that the optical disk 1 is notrecorded, wherein the microscopic construction 10 is a physical formatof the optical disk 1. In FIG. 2, the microscopic construction 10comprises a plurality of grooves 11 a through 11 d, hereinafterrepresented by a groove 11, a plurality of lands 12 a through 12 c,hereinafter represented by a land 12 and a plurality of address pits 13a and 13 b, hereinafter represented by an address pit 13. Further, awidth of each groove 11 is “w” and each groove 11 is allocated withkeeping a space of track pitch TP to an adjoining groove and a length ofthe address pit 13 is AL. The grooves 11 a through 11 d are formed onthe substrate 2 approximately in parallel to each other. Each groove 11is deflected by a frequency of integral multiples of a sync-framefrequency of a whole system so as to extract a clock frequency, andformed as a sinusoidal waveform. The waveform can be in synchronism withor asynchronism with adjacent grooves.

The address pit 13 is formed with being scattered in the lands 12 athrough 12 c between the grooves 11 a through 11 d and loaded with anaddress information. In other words, the address pit 13 is previouslyembedded in the substrate 2 so as to bridge adjoining tracks in an “I”shape. The groove 11 sinusoidally deflected and the address pit 13allocated with scattering between the grooves is formed in a same depth.Since the address pit 13 bridges the adjoining grooves, the address pit13 can be read out while using either one of adjoining grooves. In otherwords, it is defined arbitrarily whether an address of a groove isdefined by an inner circumference area or an outer circumference area ofthe groove. The address pit 13 is allocated at a position, wherein thesinusoidal groove 11 is deflected maximally, that is, within ±10 degreesat a peak point of a sinusoidal waveform.

An address information is recorded in accordance with a distance betweeneach address pit 13. Accordingly, the length AL of the address pit 13itself is kept constant.

FIG. 17 shows a physical construction format as one example of anaddress information.

In FIG. 17, a sync-bit or a synchronous signal is allocated at a head ofthe format and followed by a relative address data and an errorcorrection code (ECC) block address data. The format is composed of, forexample, one bit of the sync-bit, 4 bits of the relative address dataand 8 bits of the ECC block address data.

FIG. 3 is another fragmentary plan view of a physical format of theoptical disk 1 shown in FIG. 1, partially enlarged, and shows typicallya state of that the optical disk 1 is recorded. In FIG. 3, aconfiguration of the microscopic construction 10 is basically a same asthat of FIG. 2. However, a recording mark 14 having a length of ML isrecorded in the groove 11 in deflective. The recording mark 14 is aphase change recording, that is, recorded by changing of a material ofthe recording layer 3 such that a state of not recorded is a nature ofcrystalline and a state of recording is a nature of amorphous, forexample. The recording mark 14 can be reproduced by utilizing a highreflectivity in crystalline and a low reflectivity in amorphous. On thecontrary, it can be recorded such that the state of not recorded is in alow reflectivity and the state of recorded is in a high reflectivity byselecting a material.

The recording mark 14 is a modulated signal composed of a digital codecommonly known and is a signal having a mark length ML of integralmultiples of a channel bit “T”. Accordingly, all signals of which ashortest mark length is assigned to 2T, 3T, 4T or 5T can be handled as asame manner as an optical disk commonly available. For example, in asignal system assigning a shortest mark length to 3T, a signal systemcomposed of signals of 3T through 11T such as 8-14 modulation, 8-15modulation and 8-17 modulation and another signal system composed ofsignals of 3T through 11T such as 8-16 modulation and a further signalsystem composed of a 14T signal can be handled.

In the optical disk 1 of the embodiment of the present invention, asmentioned above, the address pit 13 is recorded with being scattered onthe land 12. An inherent area 24 shown in FIG. 19 for the land-groovemethod is not provided, so that an area utilizing efficiency of theoptical disk 1 is superior to that of a disk of the land-groove method.Further, the recording mark 14 is recorded in the groove 11, so that theconstruction of the optical disk 1 is low in interference with theaddress pit 13 on the land 12. However, in some cases, the address pit13 is adjacent to the recording mark 14 as shown in FIG. 3, so that itis necessary to pay attention to readability of the address pit 13 andthe recording mark 14 after recorded in adjacent to each other.

With respect to a material of the recording layer 2 utilized for theoptical disk 1 of the present invention, a material of phase change suchthat a reflectivity of the recording layer 2 is more than 15% issuitable, preferably, more than 18% of high reflectivity is moresuitable. Particularly, an alloy including antimony, tellurium and ametal having a melting point of less than 1100 degrees centigrade, andhaving a high contrast of reflectivity between before recording andafter recorded is suitable for the material of the recording layer 2. Asfor a material having a practical recording sensitivity and signalcharacteristics such as degree of modulation, reflectivity, jitter and anumber of rewritable possibilities, a material including antimony andtellurium as essential components and further including at least one ofgold, silver, copper, indium, aluminum and germanium is desirable.Particularly, silver-indium-antimony-tellurium (AgInSbTe) alloy,copper-aluminum-tellurium-antimony (CuAlTeSb) alloy,silver-germanium-antimony-tellurium (AgGeSbTe) alloy andgold-germanium-antimony-tellurium (AuGeSbTe) alloy are most desirablematerials.

Dimensions are defined for a purpose of explaining recording/reproducingperformances, which will be described hereafter. In FIG. 2, a distancebetween center lines of one groove and its adjoining groove is definedas a track pitch “TP”, wherein grooves 11 a through 11 d aresinusoidally deflected, and a width of the groove 11 itself is definedas “w” and a length of the address pit 13 is defined as “AL”. Theaddress pit 13 is driven into approximately a center of the land 12, sothat a space between centerlines of the address pit 13 and the groove 11is approximately 2/TP, not shown. Further, the groove 11 and the addresspit 13 are engraved on the substrate 2 in a same depth respectively andthe depth is “d”, not shown. Furthermore, in FIG. 3, a length of therecording mark 14 after recorded, varies by modulation. However, ashortest mark length is defined as “ML”.

By using phase change materials for high density recording mentionedabove, trial optical disks having various dimensions (TP, d, w, ML andAL) of microscopic construction are manufactured and theirrecording/reproducing characteristics are evaluated. According to theevaluations, a most suitable numerical range of address output anddimensional range of the microscopic construction of the optical disk 1of the embodiment of the present invention can be obtained. In additionthereto, an actual length of “TP” and “ML” are assumed to beapproximately 60 to 70% and 35 to 45% of a reproduction spot diameterλ/NA of a laser beam respectively for an optical disk and its driveexplained as the embodiment of the present invention.

Results of evaluation on trial optical disks for recording/reproducingcharacteristics are as follows:

(1) Tracking Performance of a Disk not recorded

In a case of a disk after recorded, as shown in FIG. 3, the recordingmark 14 having a different reflectivity is formed in the groove 11, sothat various methods can be applied to a tracking method of a diskrecorded. For example, the DPD (Differential Phase Detection) and theDPP (Differential Push-Pull) tracking methods are available. However, ina case of a disk not recorded, as shown in FIG. 2, no recording mark isformed in the groove 11. Accordingly, only the push-pull method can beapplied to a tracking method of a disk not recorded actually.

A relationship between the depth “d” of the groove 11 and a push-pullsignal output PPb is examined and indicated in FIG. 4, wherein therelationship is measured over a range from 0.35 to 0.55 of the ratio ofthe groove width “w” to the track pitch TP (w/TP). As shown in FIG. 4,the shallower the depth “d” is, the smaller the PPb is. The PPb ismaximized at d=0.125 λ/n, wherein “n” is a refractive index of a lightpath. The tracking itself is stable even at a smaller PPb. A limit ofbeing out of tracking is actually examined for a phase change type disk1 having scattered address pits according to the present invention. Thelimit is PPb=0.22. The tracking is stable in an area where PPb is morethan 0.22. In other words, it is necessary for the depth “d” to satisfyan equation d≧0.05 λ/n.

(2) Reproduction Performance of Recording Mark

A jitter is one of indexes representing readout performance of therecording mark 14. While reproducing after recorded, a fluctuation in atime axis direction or a standard deviation divided by a clock frequencyis a jitter. The smaller a jitter value is, the more stable areproduction is. According to the DVD standard, a jitter value isprescribed to not more than 8.0% after passing through an equalizer.

FIG. 5 shows a jitter value measured in response to a depth and a widthof the groove, in a case of 5 tracks and 10 times over written. In FIG.5, a groove width is represented by w/TP, which is a value ofprescribing the width “w” to the track pitch TP. As shown in FIG. 5, theshallower the groove depth “d” is, the better a jitter is obtained. Thereason is that the shallower the groove depth “d” is, the higher areflectivity and a modulation factor of signal can be obtained, and thenbase noise decreases relatively. An effect of w/TP on a jitter isrelatively low.

In order to obtain a jitter of not more than 8.0%, it is necessary forthe depth “d” to satisfy an inequality d≦0.1 λ/n although it dependsupon a groove width. Further, it is also necessary for the w/TP tosatisfy an inequality 0.35≦(w/TP)≦0.55. In addition thereto, the addresspit 13 is formed as an “I” shape against each groove, so that a width ofthe address pit 13 is assigned to be a value from 0.65 to 0.45 inproportion to the TP.

(3) Reproduction Performance of Address Pit and Interference with theAddress Pit by Recording Mark

A pickup installed in a reproducing apparatus such as a DVD player isequipped with a 4 division photo detector. The 4 division photo detectorcan effectively produce an address signal by arithmetically calculatingsuch as adding, subtracting, multiplying and dividing four output fromeach segment of the 4 division photo detector.

FIG. 6 shows a typical 4 division photo detector 9 mentioned above. InFIG. 6, a vertical axis and a horizontal axis are defined as a radialdirection and a tangential direction or a track direction respectivelywith corresponding to FIGS. 2 and 3. Four reproduction output of the 4division photo detector 9 are assigned as Ia, Ib, Ic and Idrespectively. The Ia and Ib are allocated in an innermost circumferencearea and the Ic and Id are allocated in an outermost circumference areawith corresponding to FIGS. 2 and 3. The address pit 13 can bereproduced in high contrast by composing output as an equation(Ia+Ib)–(Ic+Id).

FIG. 7 shows a reproduced waveform in a state of not recorded.

FIG. 8 shows a reproduced waveform in a recorded state.

In FIG. 7, the waveform is reproduced with superimposing a waveform ofthe address pit 13 with a waveform of the groove 11 sinusoidallydeflected. As shown in FIG. 7, the address pit 13 can be detected as apulse projected from the total waveform, so that an address can be readout. Accordingly, a standardized value in response to a height of thepulse can be defined as an output of an address pit in a not recordedstate. Actually, a number of dividing an absolute value of(Ia+Ib)–(Ic+Id) by a total output of a 4 division photo detector, thatis, (Ia+Ib+Ic+Id) is defined as an address pit output (APb) in a notrecorded state. The APb means a value of address pit signal componentoccupying in a reproduced signal in a not recorded state. In otherwords,APb=|(Ia+Ib)−(Ic+Id)|/|(Ia+Ib+Ic+Id)|

In a case of measuring more accurately, a filter is desired to beinserted so as to eliminate various noise components. In a case ofmeasuring an absolute value of (Ia+Ib+Ic+Id), for example, a low passfilter having a cut off frequency of 30 kHz shall be inserted. In a caseof measuring an absolute value of (Ia+Ib)−(Ic+Id), an amplifier having afrequency range of more than 20 MHz is desired to be used.

An address pit output value is obtained by a diffraction of the addresspit 13, so that the address pit output value closely depends upon thedepth “d” and the length AL of the address pit 13. An address pit outputvalue APb is hardly read out if the output value is too small.Accordingly, an error rate is apt to increase.

In FIG. 8, a signal of the recording mark 14 recorded in the groove 11is written over the waveform shown in FIG. 7. Since the signal of therecording mark 14 is superimposed on the groove 11 as if noise, itseverely affects reading out the address pit 13, wherein “APs” is anoutput of an address pit after recorded and “Δ” is an aperture, which isnot affected by the recorded mark. In other words, although an addresspit can be decoded in a not recorded state, in some cases, it may not bedecoded after recorded.

An optical disk produced under various combinations of the “d” and AL ismeasured up an error rate of an address pit before the optical disk isrecorded. After the measurement, the groove 11 of the optical disk isrecorded at random, and then an error rate of an address pit is measuredonce again, wherein an error rate of less than 5% after recorded is acondition of reliability.

FIG. 9 shows a measured error rate of an address pit, wherein ahorizontal axis is an address pit output value APb and a vertical axisis a block error rate BER measured up more than 1000 ECC blocks. Anerror rate before recording (BER-b) and an error rate after recorded(BER-a) are plotted together. The larger an address pit output value APbis, the easier an address pit can be read out and the smaller an errorrate is. In comparison with before recording and after recorded, anaddress pit is easily read out before recording. However, an error isapt to happen while reading out after recorded. It is caused by that anaddress pit signal is easy to be interfered, so that enough APb value isrequired. According to facts mentioned above, in order to ensure that anerror rate is less than 5% after recorded, it is necessary for anaddress pit output value APb to be more than 0.18. In addition thereto,with minutely analyzing a state in 5% of error rate, it is commonlyobserved that an RF signal is superimposed and an aperture ratio of anaddress pit in FIG. 8, that is, Δ/APs shown in FIG. 8 is only 10%. Inother words, the Δ/APs is necessary to be more than 10%.

(4) Interference with Recording Marker by Address Pit

The address pit 13 partially contacts with the groove 11, so that it isconceivable that the address pit 13 interferes with reproduction of therecording mark after recorded. Thus, the recording mark 14 of an opticaldisk having various address pit output values (APb) is read out and anumber of errors is measured.

FIG. 10 shows a measured error rate of an recording mark, wherein ahorizontal axis is an address pit output value APb and a vertical axisis a number of PI errors, which is a number of block arrays failed inmore than one byte for continuing 8 ECC blocks. As shown in FIG. 10, thePI error suddenly increases at a certain APb value. It is conceivablethat diffraction light of the address pit 13 interferes with therecording mark 14 and a reading out error occurs. For example, accordingto the DVD standard, a number of PI error is required to be less than280, so that an address pit output value APb shall be less than 0.27.

(5) Dimensions of Microscopic Construction for obtaining desired AddressPit Output Value APb

As mentioned above, a small TP and a shortest mark length ML are assumedfor a reproduction spot diameter λ/NA of a laser beam in an optical diskand its drive according to the present invention. Further, as examinedin paragraphs (1) and (2) above, a depth “d” of a groove is assumed tobe sufficiently shallower than a reproduction wavelength of a laserbeam. Conditions of the AL and the “d” are examined to obtain a desiredaddress pit output value APb under above-mentioned conditions.

In consideration of each coherence of AL and ML, the AL and ML aresupposed to be relatively in a same order of dimension, so that they areassumed to be k=AL/ML. Relationship between the “k” and an address pitoutput value APb and relationship between the “d” and an APb areexamined. According to the examination, it becomes clear that the largerthe “d” becomes and the larger the “k” is, the larger the APb becomes.The APb can be actually expressed by a following equation: APb=0.14k+4.11 n(d−26)/λ.

As mentioned above, an address pit output APb, which does not affect anactual operation of a drive for recording and reproducing, is obtainedand further dimensions such as TP, “d”, “w” and “k” of variousmicroscopic constructions are examined. Examinations mentioned inparagraphs (1) through (5) are summarized as follows.

A range of an address pit output APb, which is an address pit signalcomponent occupying in reproduction signals in a state of not recorded,is 0.18<APb<0.27.

Dimensions of various microscopic constructions are “d”, “w” and “k”,which satisfy following relationships simultaneously.0.05 λ/n≦d≦0.1 λ/n,0.35≦(w/TP)≦0.55 and0.18<0.14k+4.11n(d−26)/λ<0.27

The optical disk 1 having an address pit output in accordance with thepresent invention can be recorded and reproduced excellently withsuppressing interactive interference between the recording mark 14 in agroove and the address pit 13 minimally. Further, the substrate 2 havingthe dimensions of microscopic construction in accordance with thepresent invention and the optical disk composed of the microscopicconstruction can minimize reproduction interference between therecording mark 14 and the address pit 13.

The present invention specifies the dimensions of a microscopicconstruction of the substrate 2 while manufacturing such the opticaldisk 1, so that stable manufacturing and supplying of the optical disk 1can be maintained. An actual manufacturing method of the optical disk 1in accordance with the present invention is depicted next with referringto FIG. 18.

FIG. 18 is a flow chart of a manufacturing method of an optical diskaccording to the present invention.

In FIG. 18, a mastering process is applied to a blank master or a resistdisk made of glass, which is commonly known, by a laser beam recorder(LBR) and the microscopic construction according to the presentinvention is formed on the blank master (Step 1001). With respect to theLBR, a recorder equipped with a laser having a wavelength such as 458,442, 413, 407, 364, 351, 325, 275, 266, 257 and 244 nm is desired.Further, a 2 beam mastering method by a master beam and a sub beam iseffective. The master beam is applied to forming the groove 11 and thesub beam is applied to forming the address pit 13. Furthermore, themaster beam is passed through a deflection device such as EOD(Electro-optic Deflector) and AOD (Acousto-optic Deflector) so as forthe master beam to be sinusoidally deflected and the sub beam is passedthrough a modulator such as an EOM (Electro-optic Modulator) and an AOM(Acousto-optic Modulator) so as for the sub beam to be intermittentlymodulated. In this mastering method by 2 beams, a positioning accuracyis insufficient if a mastering is performed individually by each beam.Therefore, it is desirable that the mastering is performedsimultaneously by 2 beams. In this case, it is necessary for a distancebetween the master beam and the sub beam to be TP/2. In additionthereto, a shape of groove does not appear in this Step 1001 although alatent image is recorded on the blank master.

The blank master recorded with an image is processed by the alkalinedevelopment, commonly known, and the mastering image is converted intoan uneven surface (Step 1002). A shape of the uneven surface hasapproximately a same as the microscopic construction 10 of the substrate2. The blank master processed by the alkaline development is hereinaftercalled a glass master. The making stamper process such as the conductiveprocess and the electroforming process, commonly known, is applied tothe glass master, and then a stamper is made (Step 1003). The stamperhas a microscopic construction approximately in reverse to that of thesubstrate 2.

By using the stamper obtained through processes mentioned above, thesubstrate 2 is composed by the commonly known forming process (Step1004). With respect to a material of the substrate 2, such syntheticresins as polycarbonate resin, polysulfone resin, polyphenylene oxideresin, polystyrene resin, polynorbornen resin, poly-methacrylic resin,polymethyl pentene resin, various copolymer and block copolymer havingresin skeleton of above-mentioned resins can be utilized. In a case ofutilizing the substrate 2 as a light path, optical characteristics suchas a refractive index “n” and birefringence of the substrate 2 shall beconsidered. By assigning the refractive index “n” to 1.45 through 1.65and the birefringence to less than 100 nm per double paths, for example,interchangeability with a DVD disk can be maintained properly.

Then the recording layer 3 is filmed over the substrate 2. Actually, therecording layer 3 is filmed over the microscopic construction 10 (Step1005). A phase change material, which is a main component of therecording layer 3, is already mentioned in the previous section.However, in order to adjust an optical characteristic and a heattransfer characteristic, the recording layer 3 can be inserted inbetween various optical interference films as required. For example,dielectric substances such as SiN, SiC, SiO, ZnS, ZnSSiO, GeN, AlO, MgF,InO and ZrO are effective, particularly, ZnSSiO (mixture of ZnS andSiO₂) is excellent in a heat balancing with a phase change material forrecording. Further, the recording layer 3 can be composed withlaminating an optical reflective film such as aluminum, gold, silver andtheir alloy together with an optical interference film so as to adjustreflectivity and a heat transfer characteristic. Furthermore, in orderto perform a high density recording/reproducing, the super resolutionmasking film and the contrast enhancing film, commonly known, can belaminated together with an optical interference film. With respect tosuch a filming method, the vacuum film forming method such as thesputtering method, the ion plating method, the vacuum evaporating methodand the CVD (Chemical Vapor Deposition) method, which are commonlyknown, can be utilized. Particularly, the sputtering method is congenialto a phase change material and excellent in mass-productivity.

A resin layer 4 is formed over the recording layer 3 succeedingly (Step1006). The resin layer 4 is provided for protecting the recording layer3 chemically and mechanically. Depending upon a construction of theoptical disk 1, adhesion can be given to the resin layer 4. With respectto a material for the resin layer 4, a resin can be selected out of suchresins as ultra violet curable resin, various radiation curable resin,electron beam curable resin, thermosetting resin, moisture curable resinand mixture of plural liquid curable resin. The commonly known methodsuch as the spin coat method, the screen printing method and the offsetprinting method can be utilized for a filming method of the resin layer4.

The construction of the optical disk 1 shown in FIG. 14 is one ofessential constructions. It is apparent that many changes, modificationsand variations in the arrangement of equipment and devices and inmaterials can be made without departing from the invention conceptdisclosed herein. For example, another substrate is adhered to theoptical disk 1 so as to increase strength of the disk. Further, twodisks of which construction is the same as that of the optical disk 1shown in FIG. 14 can be adhered to each other and formed one disk, thatis, a double face disk or a two layer disk.

[First Embodiment]

An application of the optical disk 1 of the present invention to a disksystem utilizing a semiconductor laser irradiating a red laser beam isdepicted. A wavelength λ of the red laser beam is 650 nm and a numericalaperture NA of an objective lens is 0.6. Accordingly, a reproductionspot diameter λ/NA of the laser beam is 1083 nm or 1.083 μm.

FIG. 15 is a cross sectional view of an optical disk according to afirst embodiment of the present invention.

In FIG. 15, an optical disk 100 comprises a substrate 102, a recordinglayer 103, a resin layer 104 and a dummy substrate 105 with beinglaminated in order. Embossing on a surface of the substrate 102 forms amicroscopic construction 10. The substrate 102 is a light path of alaser beam as far as the recording layer 103 and its thickness is 0.6mm. A material of both the substrate 102 and the dummy substrate 105 ispolycarbonate resin and its refractive index “n” at 650 nm is 1.58. Therecording layer 103 has a laminated construction mainly composed of aphase change material, which is in a high reflectivity when not recordedand in a low reflectivity when recorded. The recording layer 103 islaminated by ZnSSiO, AgInSbTe, ZnSSiO, and AlTi in order on thesubstrate 102 with the sputtering method. Further, its reflectivity is18 to 30%. In this construction, a recording sensitivity at 650 nm is7.5 to 14.0 mW. The recording layer 103 can also be recorded by a laserbeam of 635 nm and its recording sensitivity can be maintained in arange of 7.0 to 13.0 mW almost a same range as that of 650 nm.

The microscopic construction 10 while not recorded is shown in FIG. 2. Agroove 11 is formed spirally and its track pitch TP is 0.74 μm, which isthe same as that of a DVD-ROM (DVD-Read Only Memory) disk, and issinusoidally deflected. A period of the groove 11 is recorded by 8 timesa frequency of a sync-frame. Further, amplitude of a waveform isarbitrarily determined within a range of 9 to 17 nm. Furthermore, arespective phase among adjoining tracks is determined at random for theCLV (constant linear velocity) recording. In addition thereto, anaddress pit 13 having a certain length of AL is engraved on a landallocated outer area than the groove 11 in accordance with an addressvalue.

The microscopic construction 10 when recorded is shown in FIG. 3. Asignal to be recorded is the 8-16 modulation signal and its shortestmark length ML is 0.40 μm. The value of 0.40 μm is the same as that of aDVD-ROM disk. Accordingly, a recording capacity of 4.7 GB can berealized by a disk having a diameter of 120 mm, wherein a radius ofrecording range of the disk is 24 to 58 mm. In this recording capacity,a TP is equivalent to 68% of a reproduction spot diameter of a laserbeam and a shortest mark length ML is equivalent to 37% of thereproduction spot diameter of the laser beam.

An output range of address pit, which can perform proper recording andreproducing without interference of an recording mark 14 and an addresspit 13 in a same groove with each other, that is, a dimension of variousmicroscopic constructions, which satisfies an inequality 0.18<APb<0.27,follows a condition shown below:

0.05×650/1.58 ≦d≦0.1×650/1.58, that is, 20≦d≦41 nm and0.35≦(w/0.74)≦0.55. In other word, 0.26≦w≦0.41 μm and0.18<0.14k+4.11×1.58(d−26)/650<0.27, that is, 0.18<0.14k+0.01(d−26)<0.27, wherein ML=0.4 μm. Therefore, 0.18<0.35AL+0.01 (d−26)<0.27.In other words, it can be represented as 44<35AL+d<53.

Particularly, in order to clarify ranges of the “d” and “k”, arelationship between the “k” and APb is exhibited graphically in FIG.11. The APb is limited by d=20 nm, which is a limit of a trackingperformance, and limited by d=41 nm, which is a limit of a jitter.Accordingly, the “d” and “k” take values existing within a range of aparallelogram shown in FIG. 11. In other words, the “d” and “k” areexisted within the range enclosed by coordinates (d, k)=(41, 0.22), (41,0.85), (20, 2.34) and (20, 1.70). In consideration of scattering inmanufacturing such as a groove depth “d” and a address pit length AL,the range is desired to be enclosed by coordinates (d, k)=(39.5, 0.34),(39.5, 0.95), (21.5, 2.23) and (21.5, 1.60).

ML=0.4 μm, so that the graph shown in FIG. 11 can be rewritten withreplacing the “k” with the AL. FIG. 12 shows a graph with exhibiting thehorizontal axis with the AL. As shown in FIG. 12, according to thepresent invention, the “d” and AL are existed within a range enclosed bycoordinates (d, AL)=(41, 0.08), (41, 0.34), (20, 0.94) and (20, 0.68).In consideration of scattering in manufacturing, the range is desired tobe enclosed by coordinates (d, AL)=(39.5, 0.136), (39.5, 0.380), (21.5,0.892) and (21.5, 0.640).

[Second Embodiment]

An application of the optical disk 1 of the present invention to a disksystem utilizing a semiconductor laser irradiating a green laser beam isdepicted. A wavelength λ of the green laser beam is 532 nm and anumerical aperture NA of an objective lens is 0.75. Accordingly, areproduction spot diameter λ/NA of the laser beam is 709 nm or 0.709 μm.

FIG. 16 is a cross sectional view of an optical disk according to asecond embodiment of the present invention. In FIG. 16, an optical disk200 comprises a substrate 202, a recording layer 203, a resin layer 204and a transmission layer 207 with being laminated in order. Embossing ona surface of the substrate 2 forms a microscopic construction 10. Thetransmission layer 207 is a light path of a laser beam as far as therecording layer 203 and its thickness is 0.1 to 0.12 mm. Thetransmission layer 207 is made from acetate resin and its refractionindex “n” is 1.6. The recording layer 203 is composed of a phase changematerial, which is in a high reflectivity when not recorded and in a lowreflectivity when recorded. Further, a material of the recording layer203 is mainly CuAlTeSb having a reflectivity of 15 to 32%. Actually, therecording layer 203 is laminated by AgPdCu, ZnSSiO, CuAlTeSb and ZnSSiOin order on the substrate 202. In this construction, a recordingsensitivity at 532 nm is 4.5 to 7 mW.

The microscopic construction 10 while not recorded is shown in FIG. 2. Atrack pitch TP of the groove 11 is 0.468 μm, which is sinusoidallydeflected. A period of the groove 11 is recorded by 6 times a frequencyof a sync-frame. Further, amplitude of a waveform is arbitrarilydetermined within a range of 5 to 9 nm. Furthermore, adjoining tracksare accurately in synchronism with each other for the CAV (constantangular velocity) recording and perfectly in parallel with each other.In addition thereto, an address pit 13 having a certain length of AL isengraved on a land allocated inner area than the groove 11 in accordancewith an address value.

The microscopic construction 10 when recorded is shown in FIG. 3. Asignal to be recorded is the 8-15 modulation signal and its shortestmark length ML is 0.269 μm. Accordingly, a recording capacity of 11.8 GBcan be realized by a disk having a diameter of 120 mm, wherein a radiusof recording range of the disk is 24 to 58 mm. In this recordingcapacity, a TP is equivalent to 66% of a reproduction spot diameter of alaser beam and a shortest mark length ML is equivalent to 38% of thereproduction spot diameter of the laser beam.

An output range of an address pit, which can perform proper recordingand reproducing without interference of an recording mark 14 and anaddress pit 13 in a same groove with each other, that is, a dimension ofvarious microscopic constructions, which satisfies an inequality0.18<APb<0.27, follows a condition shown below:

0.05×532/1.60≦d≦0.1×532/1.60, that is, 17≦d≦33 nm and0.35≦(w/0.468)≦0.55. In other word, 0.16≦w≦0.26 μm and0.18<0.14k+4.11×1.60 (d−26)/532<0.27, that is, 0.18<0.14k+0.012(d−26)<0.27.

Particularly, in order to clarify a range of 0.18<APb<0.27, arelationship between the “k” and APb is exhibited graphically in FIG.13. The APb is limited by d=17 nm, which is a limit of a trackingperformance, and limited by d=33 nm, which is a limit of a jitter.Accordingly, the address pit length AL takes values existing within arange of a parallelogram shown in FIG. 13. In other words, the AL isexisted within the range enclosed by coordinates (d, k)=(33, 0.68), (33,1.32), (17, 2.68) and (17, 2.04).

While the invention has been described above with reference to aspecific embodiment relating to a high density optical disk, which isallocated with an address pit in between grooves thereof, it is apparentthat many changes, modifications and variations in the arrangement ofequipment and devices and in materials can be made without departingfrom the invention concept disclosed herein. For example, the wavelengthof the laser beam utilized for reproducing or recording/reproducing isassigned to 650 nm and 532 nm. However, the wavelength is not limited tothem. Any wavelength such as 830, 635, 515, 460, 430, 405 and 370 nm,and their nearby wavelength can be utilized. Such a numerical apertureNA of a lens as 0.4, 0.45, 0.55, 0.65, 0.7, 0.8, 0.85 and 0.9 other than0.60 and 0.75 can be utilized. Further, a numerical aperture of morethan one, which is represented by a solid immersion lens, can also beutilized.

Furthermore, in order to simplify the explanation, the microscopicconstruction shown in FIG. 2 is illustrated so as to exhibit the outlineof the present invention. Any signals other than the groove, land andaddress pit shown in FIG. 2 can be engraved on the optical disk. Forexample, a pit array carrying a lead-in signal and another pit arrayutilized for preventing an optical disk from dump copying and faking canbe recorded in an inner circumference area such as an arbitrary radiuswidth within a range with radii 15 to 24 mm for a microscopicconstruction of the substrate 2. Moreover, a write-once informationcontrol area, which is disclosed in the U.S. Pat. No. 5,617,408, calledas a BCA (burst cutting area) can be provided in an inner circumferencearea of an optical disk. In addition thereto, a thickness, an innerconstruction, outer dimensions and component materials of each layer canalso be changed or modified.

[Third Embodiment]

Two embodiments related to the optical disk 1, according to the presentinvention, comprising a substrate formed with address pits, which areallocated in sinusoidally deflected grooves and in between the grooves,a recording layer, which contains at least rewritable phase changematerial having a reflectivity of more than 15%, and a resin layerformed over the recording layer are explained and further a methodextending the present invention over the embodiments is described above.An optical disk 300, which is provided with a particular pit array ofpreventing the optical disk from a dump copying, that is, duplicatingwhole software totally in an independent area and further an address pitis embedded in the pit array, is explained next as an application.

FIG. 20 is a plan view of an optical disk according to an embodiment ofthe present invention. In FIG. 20, an optical disk 300 comprises a firstarea 311 having a first microscopic construction 111 and a second area312 having a second microscopic construction 112. The first microscopicconstruction 111 is an area of being formed with grooves sinusoidallydeflected and address pits, which are allocated with being scattered insinusoidally deflected grooves and in between the sinusoidally deflectedgrooves, and has a same microscopic construction as the microscopicconstruction 10 of the optical disk 1 according to the presentinvention. In other words, a microscopic construction while not recordedis a same construction as that of shown in FIG. 2. Further, the groove11 can be recorded and a microscopic construction when recorded is asame construction as that of shown in FIG. 3.

The second microscopic construction 112 is at least composed of addresspits, which are allocated with being scattered in a pit array and landarea. FIG. 21 is a fragmentary plan view of the second microscopicconstruction 112 of the optical disk 300, partially enlarged, while theoptical disk 300 is not recorded. In FIG. 21, a plurality of pit arrays15 a through 15 d, hereinafter represented a pit array 15 having ashortest pit length PL and a pit width “w2”, which are modulationsignals utilized for a copy guard, are engraved on the substrate 2approximately in parallel with each other and form tracks having a trackpitch TP respectively. Each pit array 15 is deflected by a frequency ofintegral multiples of a sync-frame frequency of a whole system so as toextract a clock frequency and formed as a sinusoidal waveform. Thewaveform can be in synchronism with or asynchronism with adjacent pitarrays. An address pit 13 is engraved with being scattered in betweentracks, that is, in the land area 12 and carries an address information.In other words, the address pit 13 is formed in the land area 12, sothat the address pit 13 can be read out by a reproducing apparatus and arecording/reproducing apparatus equipped with the 4 division detector 9as same manner as that for the aforementioned optical disk 1. Theaddress information is recorded in accordance with a distance betweeneach address pit 13. Therefore, a length AL2 of the address pit 13 isassumed to be constant. FIG. 17 is an information format exhibiting oneexample of an address information. A sync-bit or a synchronous signal isallocated at a head of the information format and followed by a relativeaddress data and an ECC (error correction code) block address data. Theformat is composed of, for example, one bit of the sync-bit, 4 bits ofthe relative address data and 8 bits of the ECC block address data. Itis arbitrarily defined whether an inner circumference side or an outercircumference side of the pit array 15 is assigned to be an address ofthe pit array 15. Further, the address pit 15 is allocated at aposition, where the sinusoidal groove 11 is maximally deflected, thatis, within 10 degrees from a peak of the sinusoidal waveform. Both thepit array 15 and the address pit 13 are a same depth d2 (not shown).

The optical disk 300 of the present invention comprises two individualmicroscopic constructions, that is, the first microscopic construction111 and the second microscopic construction 112 and they can bearbitrarily allocated. In other words, they can be allocated in eitheran inner circumference area or an outer circumference area. Further, itcan be feasible that the second microscopic construction 112 iscontained in the first microscopic construction 111. A perpendicularsectional construction of the optical disk 300 at least comprises asubstrate 2, a recording layer 3 and a resin layer 4 as same as that ofthe optical disk 1. Any construction shown in FIGS. 14 through 16, forexample, can be applicable for the optical disc 300. Furthermore, therecording layer 3 contains at least a phase change recording materialand its reflectivity is more than 15%. It is acceptable that the firstmicroscopic construction 111 and the second microscopic construction 112are different from each other in physical parameters such as differenttrack pitches TP and TP2, different depths “d” and “d2” and differentwidths “w” and “w2”. However, it is desired that some parameters are asame so as to simplify a system and to manufacture the optical disk 300easier. It is more desired that all the parameters are the same. Withrespect to an address information to be engraved, it is desired that thefirst and the second microscopic constructions 111 and 112 share oneconsistent table and utilize the table not so as to be overlapped eachother.

The first area 311 or the first microscopic construction 111 of theoptical disk 300 is an area for recording and reproducing as same asthat of the aforementioned optical disk 1, so that an addressinformation is necessary to be read in either states of not recorded orrecorded. Further, an interference of the address information with arecording signal shall be considered. Accordingly, a signal output,which complies with the aforementioned conditions (1) through (4), anddimensions of a microscopic construction are necessary for reading outan address information.

On the other hand, the second area 312 or the second microscopicconstruction 112 of the optical disk 300 is another area for preventingthe optical disk 300 from dump copying and each dimension of the secondmicroscopic construction 112 is prescribed so as for a system to brakedown when a malicious person tries to record in the second area 112. Ina case that dimensions of the second area 312 are almost a same as thoseof the first area 311, for example, signals from both areas are mixedand either signals can not be read out by writing in for a dump copying.With prescribing TP2=TP, it is a most ideal case that PL=ML.

With assuming such an illegal copying, it is not necessary forreadability of the address pit 13 after recorded or dump copied to beconsidered. However, it is necessary for an address information to beaccurately read out while not recorded. As seen from FIG. 21, one pit ofthe pit array 15 and the address pit 13 are a similar signal, so that itis necessary for a signal output of the address pit 13 to exceed that ofthe pit array 15.

While the optical disk 300 is not recorded, the readability of theaddress pit 13 of the second area 312 (the second microscopicconstruction 112) is observed by using the 4 division detector 9 shownin FIG. 6 and by reproducing the composite output (Ia+Ib)−(Ic+Id) fromthe 4 division detector 9. FIG. 22 shows a reproduced waveform, which isobtained such that the composite output (Ia+Ib)−(Ic+Id) is passedthrough an amplifier having a bandwidth of 20 MHz or more. As shown inFIG. 21, the address pit 13 is superimposed on a sinusoidally deflectedtrack and a waveform composed of the pit array 15 and the address pit 13is reproduced. An address can be read out from the composed waveform ifthe address pit 13 can be detected out from the composed waveform. Areadout performance of an address depends upon an output of the addresspit 13: the larger the output and the smaller a leakage from the pitarray 15, the better the performance can be obtained. Accordingly, thelarger an aperture ratio of the address pit shown in FIG. 22 is, thelower in error rate the signal is. An aperture ratio in the second area112 is prescribed to “R” and defined as R=Δ2/AP2. In order to obtaincorrelation between the aperture ratio “R” and an error rate of theaddress pit 13, several types of the optical disk 300 are produced withvarying the parameter AL2 as a trial. Further, pit arrays are modulatedby the 8-16 modulation method and a pit 15Z adjoining to the address pit13 shown in FIG. 21 is arranged to be 14T, wherein “14T” is thesync-signal. An error rate of the address pit 13 in a trial disk, whichis manufactured as mentioned above, is measured while the trial disk isnot recorded.

FIG. 23 shows a measured error rate of an address pit in the second area112 of the optical disk 300. The horizontal axis is the aperture ratio“R” of an address pit and the vertical axis is a block error rate (BER)measured up more than 100 ECC blocks. Further, it is one condition ofreliability that an error rate shall be 3% or less while the disk is notrecorded. As shown in FIG. 23, the larger value the aperture ratio “R”of the address pit is, the easier the address pit can be read out andthe smaller the error rate is. In order to maintain an error rate of 3%or less, it is found that the aperture ratio “R” of an address pit shallbe 0.3 or more, that is, 30% or more.

An address pit performance, which ensures actual operation of a drivefor recording and reproducing the optical disk 300 and which is studiedas mentioned above, is summarized as follows. In other words, aperformance index of an address pit signal in a not recorded state shallsatisfy following conditions.

The first area 311 (first microscopic construction 111): 18<APb<0.27

The second area 312 (second microscopic construction 112): R>0.3

Microscopic dimensions, which satisfy a performance of the address pitsignal mentioned above, particularly, microscopic dimensions of thesecond area 312 are hard to specify due to too many parameters. However,a limiting range of the second area 312 is rather wider in comparisonwith that of the first area 311, which requires that respective addresserror rate shall be maintained on both recording and reproducing.Further, since parameters of the first and second areas 311 and 312 aredesired to be common as far as possible, an limiting range of the firstarea 311 shall be examined whether or not it is applied to the secondarea 312 as it is with respect to each case. It is better to modifypartially, if necessary. However, in most cases, it is possible to applythe limiting range of the first area 311 to the second area 312 as itis.

[Fourth Embodiment]

An application of the optical disk 100 of the present invention to adisk system utilizing a semiconductor laser irradiating a red laser beamis depicted. A wavelength λ of the green laser beam is 650 nm and anumerical aperture NA of an objective lens is 0.6. Accordingly, areproduction spot diameter λ/NA of the laser beam is 1083 nm or 1.083μm.

A cross sectional view of an optical disk 100 is shown in FIG. 15. Theoptical disk 100 is a single side disk and can be recorded on andreproduced from either side of the disk. A first and second microscopicconstructions 111 and 112 are engraved on a surface of the substrate102. The substrate 102 is a light path of a laser beam as far as therecording layer 103 and its thickness is 0.6 mm. A material of thesubstrate 102 is polycarbonate resin and its refractive index “n” at 650nm is 1.58. The recording layer 103 has a laminated construction mainlycomposed of a phase change material, which is in a high reflectivitywhen not recorded and in a low reflectivity when recorded. The recordinglayer 103 is laminated by ZnSSiO, AgInSbTe, ZnSSiO, and AlCr in order onthe substrate 102 with the sputtering method. An optical disk 100 ismanufactured in accordance with a manufacturing method shown in FIG. 26.The manufacturing method is similar to that of shown in FIG. 18, so thatmanufacturing steps common to those of FIG. 18 are omitted. A dummysubstrate 105 having a thickness of 0.6 mm is prepared (Step 1007) afterfilming a recording layer 103 on a substrate 102 (Step 1005). The dummysubstrate 105 is adhered to a lamination of the recording layer 103 andthe substrate 102 with sandwiching a resin layer 104 between therecording layer 103 and the dummy substrate 105 (Step 1008), and thenthe optical disk 100 is manufactured. In this construction, a recordingsensitivity of the recording layer 103 at 650 nm is 7.5 to 14.0 mW. Therecording layer 103 can also be recorded by a laser beam of 635 nm andits recording sensitivity can be maintained in a range of 7.0 to 13.0 mWalmost a same range as that of 650 nm.

FIG. 25 is a plan view of an optical disk 400 according to the fourthembodiment of the present invention. As shown in FIG. 25, the opticaldisk 400 comprises a first area 411 a having the first microscopicconstruction 111, a second area 412 having the second microscopicconstruction 112 and another first area 411 b having the firstmicroscopic construction 111. In other words, the optical disk 400comprises the first areas 411 a and 411 b having the first microscopicconstruction 111 for recording and reproducing and the second area 412having the second microscopic construction 112 for preventing theoptical disk 400 from dump copying. The first areas 411 a and 411 b arean area, which is engraved with the groove 11 for recording andreproducing and the address pit 13 as shown in FIG. 2. The second area412 is another area engraved with the specific pit array 15 forpreventing the optical disk 400 from dump copying and the address pit 13as shown in FIG. 21. Actually, the optical disk 400 comprises the firstarea 411 a, the second area 412 and the first area 411 b in order fromthe innermost circumference area to the outermost circumference area.

The groove 11 having a width of “w” is provided spirally in the firstareas 411 a and 411 b and its track pitch TP is 0.74 μm as same as thatof a DVD-ROM disk and sinusoidally deflected. A period of the groove 11is recorded by eight times a sync-frame frequency. Further, amplitude ofa waveform of the groove 11 is arbitrarily prescribe within a range of 9to 17 nm. Furthermore, a respective phase among adjoining tracks isdetermined at random for the CLV (constant linear velocity) recording.Moreover, an address pit 13 having a certain length of AL is engraved ona land allocated outer area than the groove 11 in accordance with anaddress value. In addition thereto, a depth of the groove 11 is a sameas that of the address pit 13 and the depth is “d” respectively.

The specific pit array 15 having a width of “w2” is also providedspirally in the second area 412 and its track pitch TP2 is 0.74 μm assame as that of the first area 411 and sinusoidally deflected. A periodof the groove is recorded by eight times a sync-frame frequency.Further, amplitude of a waveform of the groove is arbitrarily prescribedwithin a range of 9 to 17 nm. Furthermore, a respective phase amongadjoining tracks is determined at random for the CLV (constant linearvelocity) recording. Moreover, an address pit 13 having a certain pitlength of AL2 is engraved on a land allocated outer area than thespecific pit array 15 in accordance with an address value. A depth ofthe specific pit array 15 is a same as that of the address pit 13 andthe depth is “d2”. In addition thereto, the specific pit array 15 ismodulated by the 8-16 modulation method and its shortest pit length PL,that is, the 3T signal is 0.40 μm. Each address pit 13 is provided withthe pit 15 z composed of the 14T signal with being adjacent to theaddress pit 13.

The microscopic construction 111 in the first areas 411 a and 411 b isshow in FIG. 3 while the optical disk 400 is recorded. A signal isrecorded within the groove 11 and its recording mark 14 is a signal ofthe 8-16 modulation method. Further, a shortest mark length ML is 0.40μm. In this case, the TP or the TP2 is equivalent to 68% of areproduction spot diameter of a laser beam and a shortest mark lengthML, that is, the PL is equivalent to 37% of the reproduction spotdiameter of the laser beam.

In the first area 411, an output range of address pit, which cansuppress an interference between an recording mark 14 in the groove 11and an address pit 13 minimally, that is, a dimension of variousmicroscopic constructions, which satisfies an inequality 0.18<APb<0.27,follows a condition shown below as same as that of the first embodiment:20≦d≦41 nm and 0.35≦(w/0.74)≦0.55, and further, 44<35AL+d<53.

A range of the “d” and AL to realize the above inequality is existedwithin a parallelogram shown in FIG. 12. In other words, the “d” and ALare existed within the range enclosed by coordinates (d, AL)=(41, 0.08),(41, 0.34), (20, 0.94) and (20, 0.68).

With respect to the second area 412, it is examined whether or not thesemicroscopic dimensions can be applied, next. Trial optical disks aremanufactured with varying each w2/TP2, that is, w2/0.74 of 4 coordinatesof the parallelogram from 0.35 to 0.55, and then the disks are measuredwith an aperture ratio “R” of the second area while not recorded and itserror rate, which is a block error rate measured with more than 100 ECCblocks. A result of the measurement is shown in Table 1. As shown inTable 1,it is apparent that the “R” takes values from 0.45 to 0.75 atd2=20 nm and takes values from 0.48 to 0.78 at d2=41 nm. These valuesare all in R>0.3 and a measured error rate is less than 2.3%.Accordingly, sufficiently low error rate can be obtained. In otherwords, the microscopic dimensions such as “d2”, “w2” and AL2 in thesecond area 412 can be defined as a same range as those of the firstarea 411. Therefore, there is no difficulty in a system design forreproducing two areas.

TABLE 1 BER d2 (nm) AL2 (μm) w2/TP2 R (%) 20 0.680 0.35 0.45 2.3 200.680 0.45 0.49 2.0 20 0.680 0.55 0.54 1.5 20 0.940 0.35 0.66 1.0 200.940 0.45 0.70 0.8 20 0.940 0.55 0.75 0.5 41 0.134 0.35 0.48 2.3 410.134 0.45 0.55 1.2 41 0.134 0.55 0.60 0.9 41 0.340 0.35 0.68 0.8 410.340 0.45 0.73 0.5 41 0.340 0.55 0.78 0.4 TP1 = TP2 = 0.74 (μm), ML =PL = 0.40 (μm)[Fifth Embodiment]

An application of the optical disk 100 of the present invention to adisk system utilizing a semiconductor laser irradiating a red laser beamis depicted. A wavelength λ of the green leaser beam is 650 nm and anumerical aperture NA of an objective lens is 0.6. Accordingly, areproduction spot diameter λ/NA of the laser beam is 1083 nm or 1.083μm.

FIG. 24 is a cross sectional view of an optical disk 500 according to afifth embodiment of the present invention. As shown in FIG. 24, theoptical disk 500 is a double face disk and either face of the disk canbe reproduced. The optical disk 500 is manufactured in accordance with amanufacturing method shown in FIG. 27. As shown in FIG. 27, twointermediate disks composed of a substrate 502 and a recording layer 503are produced (Step 1005). The intermediate disks are adhered togetherwith sandwiching a resin layer 504 between them so as to face eachrecording layer 503 toward each other (Step 1018), and then the opticaldisk 500 is finally manufactured.

The first and second microscopic constructions 111 and 112 are formed ona surface of the substrate 502 with being embossed. The substrate 502 isa light path of a laser beam as far as the recording layer 503 and itsthickness is 0.6 mm. A material of the substrate 502 is polycarbonateresin and its refractive index “n” at 650 nm is 1.58. The recordinglayer 503 has a laminated construction mainly composed of a phase changematerial, which is in a high reflectivity when not recorded and in a lowreflectivity when recorded. The recording layer 503 is laminated byZnSSiO, AgInSbTe, ZnSSiO, and AlCr in order on the substrate 502 withthe sputtering method. A reflectivity of the recording layer 503 is 18to 30%. In this construction, a recording sensitivity of the recordinglayer 503 at 650 nm is 7.5 to 14.0 mW. The recording layer 503 can alsobe recorded by a laser beam of 635 nm and its recording sensitivity canbe maintained in a range of 7.0 to 13.0 mW almost a same range as thatof 650 nm.

A microscopic construction while not recorded is the same configurationshown in FIG. 25. As shown in FIG. 25, the optical disk 500 comprisesthe first areas 411 a and 411 b having the first microscopicconstruction 111 for recording and reproducing and the second area 412having the second microscopic construction 112 for preventing theoptical disk 500 from dump copying. The first areas 411 a and 411 b arean area, which is engraved with the groove 11 for recording andreproducing and the address pit 13 as shown in FIG. 2. The second area412 is another area engraved with the specific pit array 15 forpreventing the optical disk 500 from dump copying and the address pit 13as shown in FIG. 21. Actually, the optical disk 500 comprises the firstarea 411 a, the second area 412 and the first area 411 b in order fromthe innermost circumference area to the outermost circumference area.

The groove 11 having a width of “w” is provided spirally in the firstareas 411 a and 411 b and its track pitch TP is 0.74 μm as same as thatof a DVD-ROM disk and sinusoidally deflected. A period of the groove 11is recorded by eight times a sync-frame frequency. Further, amplitude ofa waveform of the groove 11 is arbitrarily prescribed within a range of9 to 17 nm. Furthermore, a respective phase among adjoining tracks isdetermined at random for the CLV (constant linear velocity) recording.Moreover, an address pit 13 having a certain length of AL is engraved ona land allocated outer area than the groove 11 in accordance with anaddress value. In addition thereto, a depth of the groove 11 is a sameas that of the address pit 13 and the depth is “d” respectively.

In the second area 412, the specific pit array 15 having a width of “w2”is provided spirally in a same direction of rotation as that of thefirst area and its track pitch TP2 is 0.74 μm as same as that of thefirst area and sinusoidally deflected. A period of the groove isrecorded by 8 times a sync-frame frequency. Further, amplitude of awaveform of the groove is a same as that of the first area 411.Furthermore, a respective phase among adjoining tracks is determined atrandom for the CLV (constant linear velocity) recording. Moreover, anaddress pit 13 having a certain pit length of AL2 is engraved on a landallocated outer area than the specific pit array 15 in accordance withan address value as same as that of the first area. A depth of thespecific pit array 15 is a same as that of the address pit 13 and thedepth is “d2”. In addition thereto, the specific pit array 15 ismodulated by the 8-16 modulation method and its shortest pit length PL,that is, the 3T signal is 0.40 μm. Each address pit 13 is provided withthe pit 15 z composed of the 14T signal with being adjacent to theaddress pit 13.

Actual dimensions of the first and second areas for manufacturing areprescribed with 20≦d≦41 nm, 0.35≦(w/0.74)≦0.55 and 44<35AL+d<53.Further, for easier manufacturing, parameters are prescribed as d2=d,w2=w and AL2=AL.

An address pit 13 of the optical disk 500 manufactured as mentionedabove can be read out properly from the first and second areas while thedisk 500 is not recorded. Further, the first area is recorded with themicroscopic construction 111 shown in FIG. 3. In other words, a 8-16modulation signal having the shortest mark length ML of 0.40 μm isrecorded in the groove 11 as a recording mark 14. In this case,readability of the address pit 13 is excellent. In addition thereto, therecording mark 14 can be reproduced properly.

According to an aspect of the present invention, there provided anoptical information recording medium, which is realized as an opticaldisk for high density recording by utilizing a phase change recordinglayer having reflectivity of more than 15% together with an address pit,which is recorded on a land with being scattered. Particularly, such adisk having an address pit output in accordance with the presentinvention can minimize relative interference between a recording markprovided in a groove and an address pit signal and can be recorded andreproduced excellently. Further, dimensions of microscopic constructionof a disk substrate are specified, so that stable manufacturing andsupplying of a disk can be maintained.

According to another aspect of the present invention, there provided anoptical information recording medium, which is a high density phasechange type optical recording disk having a recording/reproducing arearecorded with an address pit with scattered on a land and having anotherarea recorded with a pit array for preventing the disk from illegalcopying and a scattered address signal together. Further, by prescribingan aperture ratio of an address signal within a specific range, the diskcan be read out in a low error rate. Furthermore, in order to realizethe readout in a low error rate, a microscopic construction of a disksubstrate is specified by dimensions. Accordingly, stable manufacturingand supplying of a disk can be assured.

1. An optical information recording medium comprising: a substrateformed with an area having sinusoidally deflected grooves and addresspits scattered and allocated between said grooves; a recording layerhaving reflectivity of more than 15%; and a resin layer formed over saidrecording layer, said optical information recording medium is furthercharacterized in that an output value of address pit as a signalcomponent of address pit occupying in a reproduced signal under a notrecorded condition in said area is within a range of 0.18 to 0.27.
 2. Anoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected grooves and address pits scatteredand allocated between said grooves of which a track pitch TP is 0.74 μm;a recording layer having reflectivity of 18 through 30% being composedof at least a rewritable phase change material; and a resin layer formedover said recording layer, said optical information recording medium isfurther characterized in that an output value of address pit as a signalcomponent of address pit occupying in a reproduced signal by using apickup having a wavelength of a laser beam of 650 nm and a numericalaperture of 0.6 under a not recorded condition in said area is within arange of 0.18 to 0.27.
 3. The optical information recording medium inaccordance with claim 2, wherein said rewritable phase change materialis an alloy containing antimony, tellurium, and a metal having a meltingpoint of less than 1100 degrees.
 4. The optical information recordingmedium in accordance with claim 2, wherein said rewritable phase changematerial is a silver-indium-antimony-tellurium alloy.
 5. A reproducingmethod for reproducing an optical information recording medium, saidoptical information recording medium comprising: a substrate formed withan area having sinusoidally deflected grooves and address pits scatteredand allocated between said grooves; a recording layer havingreflectivity of more than 15% being composed of at least a rewritablephase change material; and a resin layer formed over said recordinglayer, said optical information recording medium is furthercharacterized in that an output value of address pit as a signalcomponent of address pit occupying in a reproduced signal under a notrecorded condition in said area is within a range of 0.18 to 0.27,wherein said reproducing method reproduces an optical informationrecording medium by irradiating a laser beam stopped down by anobjective lens on said recording layer.
 6. The reproducing method forreproducing an optical information recording medium in accordance withclaim 5, wherein reflectivity of a recording layer is within a range of18 to 30%.